The present invention relates to a chemically digestive agent which is usable for the release of cured photoresist films. Particularly, the invention pertains to a chemically digestive agent which can give good results when used in the production of a black matrix color television image receiving tube.
The fluorescent screen of a black matrix color television image receiving tube has such a structure as many fluorescent substance dots of the three primary colors, that is, red, blue and green are arranged on the internal surface of a glass panel and the gap between the respective fluorescent substance dots has been filled with a non-luminescent light-absorptive substance such as carbon.
Processes for the production of such a fluorescent screen of a black matrix color television image receiving tube are disclosed in many prior art references such as, for example, U.S. Pat. No. 3,558,310. A representative process of production is briefly explained below.
Cured photoresist dots having the same shape and the same size as those of fluorescent substance dots are produced on the internal surface of a glass panel at positions for the fluorescent substance dots to be formed by coating a photoresist onto the internal surface of the glass panel, drying, exposing to light through a shadow mask and then developing. A suspension of carbon is then coated onto the whole surface and dried to form a carbon film over the whole surface. The said cured photoresist dots are removed with a chemically digestive agent together with the carbon deposited thereonto. The resulting holes (which are called by "matrix holes") are respectively filled with fluorescent substances of the three primary colors, that is, red, blue and green to form fluorescent substance dots. The gap between the fluorescent substance dots is then filled up with carbon to form a fluorescent screen of a black matrix color television image receiving tube.
If the removal of the cured photoresist dots with a chemically digestive agent in the above-mentioned step of producing the fluorescent screen of the black matrix color television image receiving tube is inadequate, the shape and size of the respective fluorescent substance dots become uneven and unevenness in color occurs. Also, the carbon remains in the fluorescent substance dots, resulting in a remarkable reduction in quality of picture.
As a chemically digestive agent for removing the cured photoresist film, there has heretofore generally been used as aqueous solution of hydrogen peroxide or hypochlorous acid or a salt thereof.
Since aqueous hydrogen peroxide is weak in an activity of decomposing a cured photoresist film oxidatively, however, the shape and size of matrix holes (correspondingly fluorescent substance dots formed by filling the matrix holes) become uneven and the carbon which has remained without being removed is contained in the fluorescent substance dots in the case of hydrogen peroxide, resulting in a remarkable reduction in quality of picture.
Also, hypochlorous acid and salts thereof are excellent in an ability of removing cured photoresist films, but they are very inconvenient in practical use in that not only they generate toxic chlorine gas during operation but also they corrode remarkably the equipment and appliances for the production of a color television image receiving tube.